I share Beverly's opinion on this. Using If like she does is kind of a bit of extra "self documentation". If you later find that you really do need another Boolean expression and outcome, changing "IF" to case to add it in is trivial.

I used Case in my first response because you have two Boolean expressions.

Will not produce the same response should the value of Product Type be say: "Return" instead of "Buy/Resale" or "Commission". With the If function, it's treated as "Commission" where in the Case, you'll get an empty string (null) returned. It probably makes no difference in your case, but is a difference to be careful of in these types of functions.